It is quite common for fluid streams, such as air flow streams, gas streams and liquid streams, to carry contaminant materials therein. For example, fluid streams to engines, gas turbines, combustion furnaces, engine lube systems, hydraulic systems, coolant systems and fuel systems carry particulate contaminants therein that should be filtered.
Filtration media of various fiber compositions and processing methods are currently available for removing some or all contaminant materials from such fluid streams. The media are typically porous to permit fluid to flow through the media while at the same time trapping particulate contaminants in the media. In particular, a wide range of media have been developed for use in pleated filter elements, which expand the effective surface area of the media that can trap contaminant material. In addition to good particulate contaminant removal properties, suitable pleated filter media often have high strength, and preserve (or substantially preserve) the media's pleats during manufacture, storage and use.
In recent years, alternatives to pleated configurations have been developed, which incorporate a series of fluted sheets of media through which fluid flows from one flute to another as it passes from an upstream (“dirty”) side of the filter element to a downstream (“clean”) side of the filter element. This flow is often called “z-flow”, and filters with fluted media are sometimes referred to as a “z-flow element”. Example z-flow elements are disclosed in U.S. Pat. No. 8,241,383, assigned to Donaldson Company, Inc. In some z-flow constructions, the flutes are characterized by unique shapes that contain features such as sharp flute peaks and/or ridges formed in the fluted media between adjacent flute peaks.
Although media having structured flutes is desirable for many applications, much of the existing air filtration media can be difficult to form into structured flutes, and can become degraded (such as from tearing) during use as a result of vibrations, or the peaks and ridges (or other structures) in the flutes can fail to adequately retain their shape after forming and/or during use of the media.